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1 January 2007 Row Spacing and Seeding Rate Effects on Eastern Black Nightshade (Solanum Ptycanthum) and Soybean
Adrienne M. Rich, KAREN A. RENNER
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Reducing seeding rates in 19- or 76-cm row soybean below the optimum rate may reduce soybean competitiveness with weeds, and indirectly increase production costs to the grower. Field studies in 2001 and 2002 evaluated the effect of soybean seeding rate and row spacing on the emergence, growth, and competitiveness of eastern black nightshade (EBN) in soybean. EBN emergence ceased within 45 d after planting (DAP), and was similar across soybean seeding rates and row spacing. EBN control by glyphosate was not affected by soybean population or row spacing. Soybean planted in 19-cm rows was more competitive with EBN, regardless of seeding rate. Increasing the soybean seeding rate in 76-cm rows from 185,000 seeds/ha to 432,000 seeds/ha reduced EBN dry weight threefold at East Lansing and nearly twofold at Clarksville in 2002. There was no increase in EBN density or dry weight in 19-cm row soybean planted at 308,000 seeds/ha compared with 556,000 seeds/ha, whereas a seeding rate of 432,000 seeds/ha in 76-cm row soybean did not suppress EBN dry weight or increase soybean yield in the presence of EBN compared with a seeding rate of 308,000 seeds/ha.

Nomenclature: Glyphosate, glyphosate-resistant soybean, Glycine max (L.) Merr, eastern black nightshade, Solanum ptycanthum Dun. SOLPT

Adrienne M. Rich and KAREN A. RENNER "Row Spacing and Seeding Rate Effects on Eastern Black Nightshade (Solanum Ptycanthum) and Soybean," Weed Technology 21(1), 124-130, (1 January 2007).
Received: 21 July 2004; Accepted: 1 June 2006; Published: 1 January 2007

Application timing
canopy closure
Glyphosate-resistant crops
light interception
soybean populations
weed emergence
Weed interference
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